1. 1 Aquifers/Edwards Aquifer

2. 2 What is an Aquifer? A body of rock, sediment, or soil that contains drinkable water and can transmit this water to wells or springs in economically usable quantities

3. 3 Major Types of Aquifers 1. Unconfined (most common) 2. Confined 3. Karst: a special type that occurs in limestone rocks when a system of caves is connected and water is flowing through it. –Edwards Aquifer

4. Unconfined Aquifer Water seeps through porous materials near the surface, but is trapped by impermeable rock below.

5. Confined Aquifer Impermeable rock above and below. Rock strata must bend and outcrop at surface for rain to recharge porous material in between. Water will pressurize if higher than well heads – artesian system

6. Karst Aquifer Develops in thick limestone formations, usually in humid climates. Karst has both surface and subsurface features. http://www.watersheds.org/earth/Sinkholes.html

7. Water naturally goes underground through sinkholes to caves (solution caverns). Rainwater is slightly acidic and dissolves limestone rock to calcium carbonate & carries it away (dissolution). Causes stalactite, stalagmite, & pillar formations in caverns Karst Aquifer

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9. Source: Edwards Aquifer Authority, 2002 Edwards Aquifer Aquifer Region and Authority Boundaries

10. Edwards Aquifer in Bexar County

11. Geologic History About 17 million years ago, the aquifer rocks were uplifted and faulted, forming the Balcones Escarpment. They became subject to erosion and dissolution. http://www.watersheds.org/earth/karstmovie.htm

12. Edwards Aquifer Cross Section

13. Recharge Zone Water enters the aquifer through faults, fractures, sinkholes, or percolation through the soil. This process is called recharge. The recharge zone is the area where water enters the aquifer.

14. Caves Associated With the Edwards Aquifer Devil’s Sinkhole State Natural Area Rocksprings, TX Natural Bridge Caverns Natural Bridge Caverns, TX Kickapoo Caverns State Park Brackettville, TX Inner Space Cavern Austin, TX

15. Flowpaths of the Edwards Aquifer Why does the water flow in the direction shown in the figure? Elevation

16. The aquifer contains several flow systems – One occurs near Del Rio Flowpaths of the Edwards Aquifer

17. The largest flow system runs from near Brackettville to near Kyle…

18. … and supplies the major springs at San Marcos, New Braunfels, and San Antonio. Flowpaths of the Edwards Aquifer

19. Smaller flow systems include the Barton springs flow system… Flowpaths of the Edwards Aquifer

20. …and areas north of the Colorado River.

21. How does the water come out & who uses it? Aquarina Springs San Marcos, TX 1 Million gallons of water released from the ground per day Wells & Springs

22. Barton (main) Spring Austin, TX Austin

23. San Marcos Springs San Marcos, TX San Marcos

24. 24 Del Rio San Felipe Springs Del Rio, TX

25. Water Supply Problems

26. http://www.watersheds.org/earth/karstmovie.htm

27. Endangered Comal Springs Dryopid Beetle Comal Springs Riffle Beetle Fountain Darter Peck’s Cave Amphipod San Marcos Gambusia Texas Blind Salamander Texas wild-rice Threatened San Marcos Salamander Eight species in the Edwards Aquifer, Comal Springs, and San Marcos Springs ecosystems are currently listed by the U.S. Department of Interior, Fish and Wildlife Service, as either threatened or endangered species. Environmental Impact